The subject of the present invention is an optronic device fitted with a focusing mirror for projection on a visor. The field of the invention is the piloting of craft for which the pilot needs to be presented with information without it distracting him from his piloting, for example a sighting system with projection on the visor of the pilot helmet. The aim of the invention is to make sure that an image generator and a projection visor of an optronic device are correctly positioned one with respect to the other. That is to say that the image emitted by the image generator is correctly displayed on the projection visor. Another objective is to increase the manufacturing tolerances of the structure of the optronic device.
For reasons of weight, ergonomics and safety, a large proportion of current systems project onto a visor. Part of the visor acts as a semireflecting mirror for the optic of the visor. The shape of this visor is generally spherical or axisymmetric, therefore it functions in the same way as the power components in the optical combination of the visor. Since the visor is exposed, getting scratched and dirty, for lifetime considerations, the visor must be disconnectable. The visor is an optical component with a large surface area (angular coverage of the eye) and small thickness (weight) and made of plastic (safety and weight), it is therefore a fragile component which is easily deformed, so it is mounted onto a plastic or composite support.
The complete optical system therefore comprises an image generator which generates an image from a source or a purely synthetic image, a relay optic responsible for transmitting the light ray from this generator to the visor, which superimposes the image with the natural scenery observed directly through the visor by the user""s eyes.
The relay optic deforms the image from the image generator according to a distortion the opposite of that introduced by the inclined visor. The combination of the visor relay optic assembly then provides a distortion-free image from the image generator.
The use of high-precision mechanical and optical parts for producing the relay optic makes it possible to obtain acceptable optical performance. With regard to the visor, the problem is more difficult given its removability and its ability to deform depending on external conditions, in particular temperature. On assembly, the usual approach would consist, after putting the visor in place, in recentering the relay optic so that the image obtained on the projection visor was correct.
Another solution consists in moving the visor until it is in a position providing a correct image. This solution is acceptable for a monocular visor having only a single optical center. This is because, since the visor has a protective role to play, it must be made in one piece. If a binocular visor, therefore having two optical centers is considered, it is highly likely that once the right optical center is in place, the left optical center will not have an ideal position, hence distortions in the final image. The binocular solution is the most widespread, since at present it is this which provides the largest angular coverage, and also the best image.
The use of a binocular visor therefore requires the independent adjustment of the right and left relay optic. In this case, these adjustments are essential since the binocular superposition requirements are very strict. The tolerance of position of the visor with respect to the projection optic is, in this case, about 0.05 mm. Adjustment of these relay optic blocks involves a heavy adjusting mechanism given the required accuracy and precision constraints. This excess weight is detrimental to the safety of the wearer.
Furthermore, a difference in the position of the relay optic with respect to its theoretical position could introduce distortions due to edge effects. This is because the path of the light rays would no longer be that of the optical axis. Finally, this solution is difficult to use within the scope of a light amplification system, since in this case, the image acquisition objective lens is integral with the relay optic. All movements of this relay optic would therefore cause movement of the image acquisition objective lens and the device would then no longer face the correct direction.
The invention solves these problems by replacing the mechanical adjustment system, positioning one optical component with respect to another, with an optical adjustment system. That is to say the optical function of an optical component is positioned with respect to another, in the place expected by this other component. Mechanically, the components keep their position, it is the optical function which moves. In the invention, the movements of the optical function are provided by a plane mirror. This mirror makes sure that the relay optic sees the visor in its theoretical position, the position that the visor would have if the device was perfect. The position of this mirror can be adjusted so that the relay optic functions and the visor functions can be moved one with respect to the other.
The subject of the invention is therefore an optronic device, attached to a helmet, comprising an image source 104, a relay optic device 105, a semireflecting projection visor 108, these three components being held together by a rigid mechanical reinforcement 301 and, between the relay optic and the visor, on the optical path of rays 109 from the image source, a plane folding mirror 106, the position of which can be adjusted with respect to the reinforcement 301, characterized in that the folding mirror 106 is attached to a rigid support 304, itself connected to the mechanical reinforcement 301 by an elastic seal 307 and in that it is held under pressure via its support 304 on adjustment screws screwed into the reinforcement, these screws enabling the mirror to pivot about the axes passing through the end of two screws.